Long before South African Chris Bertish tamed a pair of monster swells to win the $50,000 first prize at the seventh Mavericks Surf Contest north of Half Moon Bay, a series of waves crashed into some of the thousands of fans who had flocked to the beach to try to see the action.

Just after 9 a.m. near Pillar Point, 13 people were injured and at least 40 people were knocked off their feet, officials said. Many of them had been standing on a short concrete wall and were thrown into rocks or mud by a surge of water.

A stage set up for an award ceremony toppled, while sound equipment meant for a beach broadcast was swamped.

The most serious injuries involved broken bones - including a man with a broken leg and a woman with a fractured ankle. Three people were taken by ambulance to local hospitals.

Wave faces up to 50 feet high

The injuries prompted authorities to evacuate one stretch of the beach and stop allowing newcomers to enter the main viewing area. Still, hundreds remained as vendors on the beach continued to sell pizza, sausages and T-shirts.

Some of the wave faces at Mavericks appeared to be more than 50 feet high. They were clean and smooth - ideal for surfing - thanks to low wind. Bertish was among those who said the waves might be the biggest ever surfed in a contest.

So big were they that they nearly knocked Bertish out in the first round. He said he was sucked back into a wave that he was trying to paddle past and was held underwater so long that he nearly blacked out.

"Finally I saw blue sky - the brightest blue sky you've ever seen in your life," said the 35-year-old Cape Town resident, who does marketing for two surf companies.

Bertish was competing in his first Mavericks event after years of trying to get in. He flew 36 hours after learning the contest had been called, leaving after work Thursday - "I didn't even pack a toothbrush," he said - and landing just after midnight Saturday.

Both of his boards didn't arrive, Bertish said, prompting a baggage handler to tell him, "Don't worry, you can just rent one."

Hoping for a view

Instead, Bertish used a board he had stashed with his friend Jeff Clark, who discovered Mavericks, first surfed it as a teenager, and co-founded the contest in 1999.

Before Bertish caught his first wave, thousands of spectators gathered at a nearby beach, arriving despite being warned by organizers that the surfers - a half-mile into the ocean - would be difficult to see. Some arrived at 4 or 5 a.m.

Organizers had provided nearby parking and shuttle buses to the beach, but had also encouraged fans to watch a Webcast or live feed on the big screen at AT&T Park in San Francisco, where admission was $25.

Hundreds clambered up hillsides trying to view the competition. Some hopped fences. But it was foggy and the waves were so big that a surfer on one wave could be obscured by the wall of water in front of him.

Many people simply sat on the beach and watched a big screen. Others stared out at the water, in the general direction of the contest.

"We're catching the Mavericks even though you can't see a friggin' thing," said Debbi Jones of Menlo Park. "Now we can say, 'I was there.' "

"I thought I might have seen a person at one point," said her husband, Conrad Jones. "But it was fleeting."

Injuries 'predictable'

The waves that injured spectators rolled in before a 10 a.m. high tide. They did not come without warning: The wall hit by a surge of water had already been covered by smaller incursions, but fans had returned to it.

One wave knocked down Betsy Foreman, 48, of Ukiah (Mendocino County), and broke her ankle. She had been part of the way up a hillside with other fans but had come down and was walking away from the water at the urging of San Mateo County sheriff's deputies.

"The wave knocked us down and washed people on top of us," said Foreman's fiance, Dan Quarles. He didn't blame organizers, saying, "You take your chances."

Mary Gram, 51, of San Rafael appeared to have a broken or dislocated middle finger on her right hand. As she waited for medical attention, she said, "I guess I'm lucky. But I lost my iPhone."

Grant Washburn, a 42-year-old surfer from San Francisco and a veteran at Mavericks, said the injuries and wrecked equipment on the beach were "absolutely predictable."

"They should never have put anything there," Washburn said. "There's a high tide with a 25-foot swell, and they set up right where the water washes over. This is why I tell my wife and kids not to come."

"That's why the engineers put a wall there," he said. "It's well documented and understood by people. You could have easily had a kid, or an adult, killed."

'Consistently bombing'

Keir Beadling, the chief executive of Mavericks Surf Ventures, said organizers will investigate what happened to see if changes need to be made. But he downplayed the injuries to spectators, saying they should have been watching on the Webcast or at AT&T Park.

"It's probably been blown out of proportion," he said on his cell phone, while riding in a boat a half-mile from the shoreline. "We're all having to deal with Mother Nature. Everybody has to exercise common sense."

The injuries, he said, "are the type of things that happen when you're out in nature. We're not in a parking lot ... to watch these guys surf in these conditions is extraordinary."

Surfer Ion Banner said the waves were "consistently bombing." In the first heat of the day, he was running out of time and needed a big score. So he paddled into a wave that he said he might have normally skipped.

"It was brutal. I free-falled 10 or 12 feet. I never even connected. My board was doing a wheelie," he said. "It was one of the 10 worst wipeouts I've ever had."

When he emerged from the "spin cycle" of the crashing wave, his nose was bleeding and his right eye was bruised. He was dizzy and felt ready to throw up. Worst of all, time was up and he was eliminated.

A majority of the surfers voted over e-mail to hold the contest Saturday after consulting weather reports and buoy readings. But some voted no, worried that the waves might be too big, wind-chopped and dangerous.

The event came after a stormy offseason in which Mavericks Surf Ventures sacked its contest director, Clark. Clark sued last month, saying he wasn't paid thousands of dollars in promised salary and royalties.